GRB 250206A

The Fermi GBM team reports the detection of a likely LONG GRB

At 19:51:31 UT on 6 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250206A (trigger 760564296.928588 / 250206827).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 222.1, Dec = -65.0 (J2000 degrees, equivalent to J2000 14h 48m, -65d 00'), with a statistical uncertainty of 1.7 degrees.

The angle from the Fermi LAT boresight is 33.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250206827/quicklook/glg_skymap_all_bn250206827.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250206827/quicklook/glg_healpix_all_bn250206827.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250206827/quicklook/glg_lc_medres34_bn250206827.gif

T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
760564296 at 19:51:31 on 06 Feb. 2025 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position is:
RA(2000.0) = 222.4 deg
Decl.(2000.0) = -63.8 deg
The 1 sigma statistical error radius is 2.6 deg.
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB250206827/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB250206827/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB250206827/json

                        

R. Gupta (NASA GSFC), S. Lopez (CNRS / IN2P3), and A. Holzmann Airasca (UniTrento and INFN Bari) on behalf of the Fermi-LAT Collaboration:

On February 06, 2025, Fermi-LAT detected high-energy emission from GRB 250206A, which was also detected by Fermi-GBM (trigger 760564296 / 250206827, GCN 39172
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 ).

The best LAT on-ground location is found to be:

RA, Dec = 225.31, -62.26 (J2000)

with an error radius of 0.56 deg (90 % containment, statistical error only). This was 33 deg from the LAT boresight at the time of the GBM trigger (T0 = 19:51:31.93 UT). The data from the Fermi-LAT shows a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 0 - 90 s after the GBM trigger is (2.1 ± 0.7) E-5 ph/cm2/s. The estimated photon index above 100 MeV is 2.1 ± 0.3. 

The highest-energy photon is a 1.4 GeV event which is observed ~ 16 seconds after the GBM trigger.

A Swift ToO has been approved for this burst.

The Fermi-LAT point of contact for this burst is Rahul Gupta (rahulbhu.c157@gmail.com).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.

D. Murphy, C. McKenna, C. de Barra, A. Ulyanov, P. McDermott, M. Doyle, R. Dunwoody, J. Mangan, G. Finneran, G. Corcoran, L. Cotter, A. Empey, J. Fisher, F. Gibson Kiely, J. Thompson, D. McKeown, A. Martin-Carrillo, L. Hanlon, S. McBreen, on behalf of the EIRSAT-1 team: 

EIRSAT-1 reports the detection of the long gamma-ray burst GRB250206A by the Gamma-ray Module (GMOD) instrument, which was also detected by Fermi GBM (GCN [39172](https://gcn.nasa.gov/circulars/39172
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 )). The detection was made starting at 2025-02-06 19:51:22.4 UTC.

The GMOD light curve for GRB250206A with 1.2s binning shows a long burst with two pulses, separated by 7.2 seconds, consistent with that seen by NASA Fermi-GBM. The 3rd softer pulse is not detected by GMOD. The spacecraft location at the time of detection was 5.095 N, 35.194 E at an altitude of 439.8 km.

The GMOD light curve for this event can be found here: 
https://grb.eirsat1.ie/250206A/250206A_LC_onboard_preliminary.png

EIRSAT-1 is Ireland’s first satellite (Doyle et al. Proceedings of the 4th SSEA, 2022). It is a 2U CubeSat and carries onboard a number of experiments including the Gamma-Ray Module (GMOD), a novel, compact, gamma-ray detector (Murphy et al, Experimental Astronomy, 53, 961–990, 2022). GMOD consists of a 25 mm × 25 mm × 40 mm Cerium Bromide scintillator coupled to SiPMs and is designed to detect gamma-ray bursts in the ~ 60 keV - 1.5 MeV range. EIRSAT-1 was developed in University College Dublin with support from ESA’s Fly Your Satellite! programme and was launched on 1st December 2023. 

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a series of observations, tiled on the sky, of the
Fermi/LAT GRB 250206A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00132

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/LAT event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.

T. Sbarrato (INAF-OAB), M. A. Williams (PSU), S. Dichiara (PSU), J.A.
Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),
A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini
(INAF-OAB) and P.A. Evans (U. Leicester) reports on behalf of the
Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 250206A in a series of observations tiled
on the sky.  The total exposure time is  4.3 ks, distributed over 10
tiles; the maximum exposure at a single sky location in the tiling was
978 s. The data were collected between T0+162.0 ks and T0+179.3 ks, and
are entirely in Photon Counting (PC) mode. 

Three uncatalogued X-ray sources have been detected, however none of
them is above the RASS limit or shows definitive signs of fading.
Therefore, at the present time we cannot identify which, if any, is the
afterglow. Details of these sources are given below:

Source 1:
  RA (J2000.0):  224.6223  =  14:58:29.34
  Dec (J2000.0): -62.7146  =  -62:42:52.5
  Error: 8.2 arcsec (radius, 90% conf.)
  Count-rate: 0.0205 [+0.0125, -0.0089] ct s^-1   
  Distance: 1996 arcsec from Fermi/LAT position.

Source 3:
  RA (J2000.0):  225.3635  =  15:01:27.23
  Dec (J2000.0): -62.3210  =  -62:19:15.4
  Error: 17.4 arcsec (radius, 90% conf.)
  Count-rate: (7.8 [+5.0, -3.6])e-3 ct s^-1   
  Distance: 236 arcsec from Fermi/LAT position.

Source 4:
  RA (J2000.0):  225.7331  =  15:02:55.95
  Dec (J2000.0): -62.5032  =  -62:30:11.4
  Error: 8.8 arcsec (radius, 90% conf.)
  Count-rate: (9.0 [+5.1, -3.7])e-3 ct s^-1   
  Distance: 1124 arcsec from Fermi/LAT position.

A catalogued source was also detected.

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00132.

This circular is an official product of the Swift-XRT team.

A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 250206A
(Fermi-GBM detection: Fermi GBM team, GCN 39172
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 ;
BALROG localization: Preis & Greiner, GCN 39173
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 ;
Fermi-LAT detection: Gupta et al., GCN 39233
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 ;
EIRSAT-1 GMOD detection: Murphy et al., GCN 39236
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 )
triggered Konus-Wind at T0=71491.594 s UT (19:51:31.594).

The burst light curve shows two multipeaked episodes
started at ~T0-3.6 s with a total duration of ~75.6 s.
The emission is seen up to ~4 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250206_T71491/

As observed by Konus-Wind, the burst
had a fluence of 2.44(-0.09,+0.10)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+9.072 s,
of 2.91(-0.44,+0.44)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+73.984 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.76(-0.10,+0.11)
and Ep = 205(-11,+13) keV (chi2 = 87/98 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.4
(chi2 = 85/97 dof).

The spectrum near the maximum count rate
(measured from T0+8.448 to T0+16.640 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.06(-0.13,+0.13)
and Ep = 223(-9,+10) keV (chi2 = 85/82 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -3.4
(chi2 = 85/81 dof).

All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.

O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 19:51:31.93 UT on 06 February 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250206A (trigger 760564296/250206827).
which was also detected by Fermi-LAT (Gupta et al. 2025, GCN 39233
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 ) and Konus-Wind (Ridnaia et al. 2025, GCN 39283
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 ).
The Fermi GBM on-ground location is consistent with the Fermi-LAT position.

The angle from the Fermi LAT boresight is 33 degrees.

The GBM light curve consists of a multipeaked emission episode followed by a single peaked emission episode with a duration (T90)
of about 64.3 s (50-300 keV). The time-averaged spectrum
from T0-2.0 to T0+79.9 s is best fit by
a Band function with Epeak = 187 +/- 8 keV,
alpha = -0.73 +/- 0.04, and beta = -2.6 +/- 0.2.

The event fluence (10-1000 keV) in this time interval is
(2.66 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.7 s in the 10-1000 keV band is 10.4 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"

M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory),  N. Werner (Masaryk U.), M. Ohno (Hiroshima U.),  L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory),  T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU)  -- the VZLUSAT-2/GRB payload collaboration.

The long-duration GRB 250206A (Fermi/GBM detection: GCN 39172
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 ; Fermi/LAT detection: GCN 39233
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 ; EIRSAT-1/GMOD detection: GCN 39236
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 ; Konus/Wind detection: GCN 39283
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 ; INTEGRAL/SPI-ACS peak detection at 2025-02-06 ~19:51:45 UTC) was detected by the GRB detectors on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by the GRB detector units no. 0 and no. 1. The detection was confirmed at the peak time 2025-02-06 19:51:43 (19:51:46) UTC. The T90 duration is 67 s (63 s) and the significance during T90 reaches 11 sigma (17 sigma) for detector unit no. 0 (no. 1).

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB250206A_GCN_VZLUSAT2.pdf

All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/
The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral.